【机械类毕业论文中英文对照文献翻译】轻量化设计的汽车零部件用高强度钢来抗凹
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机械类毕业论文中英文对照文献翻译
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毕业论文
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量化
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【机械类毕业论文中英文对照文献翻译】轻量化设计的汽车零部件用高强度钢来抗凹,机械类毕业论文中英文对照文献翻译,机械类,毕业论文,中英文,对照,文献,翻译,量化,设计,汽车零部件,强度,钢来抗凹
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Short communicationLightweight design of automobile component usinghigh strength steel based on dent resistanceYan Zhang*, Xinmin Lai, Ping Zhu, Wurong WangSchool of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200030, PR ChinaReceived 19 May 2004; accepted 14 September 2004AbstractLightweight and crashworthiness are two important aspects of auto-body design. In this paper, based on the shallow shell theory,the expression of dent resistance stiffness of double curvatured shallow shell is obtained under the concentrated load condition. Thecritical loads resulting in the local trivial dent in the center of the shallow shell is regarded as the important index for the lightweightof the automobile parts. This rule is applied to the lightweight design of bumper system by using high strength steel instead of mildsteel. The crashworthiness simulation of the lightweight part proves the validity of the lightweighting process.? 2004 Elsevier Ltd. All rights reserved.Keywords: High strength steel; Lightweight; Dent resistance1. IntroductionIn recent years, the retaining number of automobileshas been increasing steadily, which has impacted thesociety and human life greatly. Such situation leads tomany severe problems such as fuel crisis, environmentpollution. The international association of aluminumstated that petrol consumption can decrease by 810%with 10% reduction of car weight 2. Thus, automobilelightweight is a basic way to fuel saving.In order to reduce the automobile weight, there aretwo important methods 3: One, automobile parts areredesigned to optimize the structure. By using thinning,hollowing, minitype, and compound parts, car weightcan be reduced. The other, more and more lightweightmaterials, such as aluminum alloy, high strength steel,composite material, are widely used as lightweight mate-rials to replace the traditional materials like mild steel4. These materials could reduce the weight remarkably.Material replacement is generally more effective in auto-mobile lightweighting than structure modification. Withthe introduction of automobile safety legislation, crash-worthiness and safety should be considered as precondi-tions in lightweighting design of auto-body.High strength steel is widely used in automobilereplacing the traditional material of mild steel. Highstrength steel sheet can be used in auto-body to improvecomponents? impact energy absorption capacity andresistancetoplasticdeformation.Theautomobileweight can be reduced by use of high strength steel sheetof a thinner thickness to replace the mild steel sheet ofbody parts 1,3. Comparing with aluminum, magne-sium, and composite materials, high strength steel hasbetter economy in that its raw material and fabricationcost are cheaper. Besides, high strength steel can be di-rectly used in product line including forming, wielding,assembling, and painting. The operating cost can besaved since there is no need adjusting the whole line.Outside of automobile body, there are several sheetmetal Panels, most of which are shallow panels. Dentresistance is the ability to retain the shape against sunkendeflection and local dent under the external force. Dent0261-3069/$ - see front matter ? 2004 Elsevier Ltd. All rights reserved.doi:10.1016/j.matdes.2004.09.010*Corresponding author. Tel.: +86 21 62932964; fax: +86 2162933093.E-mail address: zytju (Y. Zhang)./locate/matdesMaterials and Design 27 (2006) 6468Materials& DesignResistance of automobile panels becomes an importantissue and quality criterion. Therefore, dent resistancestiffness of automobile panels should be tested and eval-uated in the process of panel design and manufacture.Some reported methods of testing are listed below 68:1. Test the displacement of sunken deflection fpunderfixed external force.2. Test the external force f to obtain fixed displacementof sunken deflection.3. Test the slope of forcedisplacement curve underexternal load.In this study, the second method will be used. The restof this paper is organized as follows: In Section 2, theexpression of dent resistance stiffness of double curva-tured shallow shell is obtained under the concentratedload condition based on the shallow shell theory. Thecritical load resulting in the local trivial dent in the centerof the shallow shell is regarded as the important evaluat-ing index for the dent resistance of the automobile parts.This rule is applied in Section 2 to the lightweighting de-sign of bumper system by using high strength steel in-stead of mild steel with crashworthiness simulation.2. Dent resistance analysis of double curvatured shallowshell2.1. Dent resistance stiffness analysis of shallow shellShell with mid surface can be characterized into threefeatures: thickness h, mid surface dimension L, curva-ture radius r, which satisfies h/r ? 1. When there existsh/L ? 1, the shell can be defined as thin shell. If L/r ? 1 is added besides the above two conditions, thethin shell is regarded as shallow shell 10.As Fig. 1 shows, the plane xy is the projection of themid surface of shallow shell along the z-axis. SupposingM is an arbitrary point on mid surface, two planesQMN & PMN are made paralleling to coordinate planeOYZ and OXZ, respectively. The two edges PM andQM can be regarded approximately as vertical becauseof mid surface?s flatness. At the same time, the lineMN is normal to mid surface. Thus, MN, QM, PMcan constitute a perpendicular reference frame MPQN,whose difference from orthogonal coordinate systemOXYZ can be ignored. And PM and QM are denotedby a and b, the curvilineal coordinate of MPQN.Assuming the Z coordinate of the point M is z, theanalytical equation of mid surface is expressed asfollows:z Fx;y:1The following equations can be obtained because of theflatness of the shell:ozox?2? 1;ozoy?2? 1;ozox?ozoy? 1:2The curvature and torsion of mid surface can be approx-imated to:kx ?o2zox2;ky ?o2zoy2;kxy ?o2zoxoy:3The Lae coefficients of mid surface along a and b direc-tions are deduced:A ds1dadxdx 1;B ds2dbdydy 1:4Applying concentrated force P along Z-axis and ignor-ing the influence of the transverse shear resultant forces,the balance differential equations of shallow shell are:oN1oxoSoy 0;oN2oyoSox 0;?kxN1 kyN2 oQ1oxoQ2oy Pd0;0 0;5Q1oM12oyoM1ox; Q2oM12oxoM2oy;where d(0,0) is Dirac-d function.The compatibility equation of shallow shell isr2N1 N2 ? Etr2kw 0;6where r2o2ox2o2oy2; r2k kxo2ox2 kyo2oy2:Expressing the moment resultants M1, M2and M12by the function of transverse displacement w, the basicequations of shallow shell under concentrated transverseforces are:Dr2r2w kxN1 kyN2 Pd0;0;r2N1 N2 ? Etr2kw 0;o2N1ox2o2N2oy2;7where N1is the membrane stress resultant in X-direc-tion; N2, the membrane resultant in Y-direction; D, thebending stiffness of shallow shell.Fig. 1. Double curvature shallow shell.Y. Zhang et al. / Materials and Design 27 (2006) 646865It is very difficult to solve above equation. Accordingto practical situation, sunken deflection will only con-centrate on a small area around external force P, so infi-nite large shallow shell 5 is assumed in this study.Because w, N1, N2are symmetric about x-, y-axis, all or-ders of derivatives of w, N1, N2become to zero at infin-ity. The following equations can be achieved by Fouriertransformation to Eq. (7):Dn2 g2 w kxN1 kyN2 P;n2 g2N1N2 ? Etkyn2 kxg2 w 0;n2N1 g2N2;8where:Z1?1Z1?1Pd0;0e?inxe?igydx dy P; w 4Z10Z10wcosnxcosgydx dy;N1 4Z10Z10N1cosnxcosgydx dy;N2 4Z10Z10N2cosnxcosgydx dy:9From Eq.(8), w can be obtained. Reverse Fourier trans-formation to w and polar coordinates transformation ton, g, w under polar coordinate system can be gainedw Pp2DZp=20Z10qcosqxcoshcosqy sinhq412t2kxcos2h kysin2h2dq dh;10Put x = 0 and y = 0 in Eq.(8), the relationship betweendeflection fpand concentrated force P of rectangle shal-low shell can be achieved as follows:P 4Et2ffiffiffiffiffiffiffiffiffikxkyp1 ? l2ffiffiffi3pfp:11Finally, dent resistance stiffness of shallow shell K isobtainedK Pfp4Et2ffiffiffiffiffiffiffiffiffikxkyp1 ? l2ffiffiffi3p :12This equation explains synthetically the relationship be-tween the dent resistance stiffness of double curvatureshallow shell and all influencing factors including mate-rial properties, geometry parameters, which can be usedto guide design, material select and manufacture.2.2. Analysis of critical load causing local trivial dentFor quantitative evaluation of critical load against lo-cal dent resistance of panels, several experience formulashave been brought forward by researchers. Based onlarge numbers of experiments, Dicellello 9 stated a for-mula that expresses minimum energy W causing visibletrivial dent trace by thickness t, yield stress rsand basicdent resistance stiffness KW Cr2st4K;13where C is proportional constant. From Eqs. (12) and(13), the critical load Pcrresulting in the local trivial dentin the center of the shallow shell can be achieved, whichis defined as the evaluating indexPcr Crst2:14From Eq. (14), there is a closely correlation betweencritical loads Pcrand thickness t, yield stress rs. The crit-ical load can be a rule to carry out lightweight design ofautomobile parts by using high strength steel instead ofmild steel.3. Example and crashworthiness analysis3.1. FE model of full car and its crash simulationA detailed finite element model has been establishedbased on a passenger car refitted from a saloon car,which is showed in Fig. 2. To ensure the correctnessand effectiveness of FE model, the following methodsare adopted:1. Since the goal is to simulate the frontal impact of thecar, the meshing of front car body is denser than thatof the rear car body.2. Reduced integration method with hourglass control istaken for 4 noded shell element and 8 noded bricksolid element to improve the efficiency of simulation.3. By using of the meshing and mass scaling technology,the characteristic length of the minimal element isensured to improve the simulation efficiency.4. Materials constitutive with CowperSymonds strainrate item is used for steel parts.5. Automaticsinglesurfacecontactalgorithmisadopted in the simulation aiming at complexity ofcar impact simulation.Fig. 2. Finite element model of full car.66Y. Zhang et al. / Materials and Design 27 (2006) 64686. Spot weld element with failure rule that consideringthe couple of normal force and shear force is used tosimulate the spot weld connection between auto parts.Explicit dynamic FEM software LS-DYNA Version950isusedtosimulatethefrontalimpactofthecaragainsta rigid wall at the speed of 50 km/s according to the Na-tional Crash Legislation CMVDR294. A real car crashexperiment is done at Car Crash Lab settled in TSingHuaUniversity.Bycomparingthetimehistoryofacceler-ation of certain position on the A pillar within 0.1 s, thesimulationgivesareasonablefittotheexperimentresults,which guaranteesthecorrectness ofFEmodel andgives anicer base for the next lightweighting optimized design.3.2. Lightweighting design and crashworthiness analysisThe use of high strength steel is one of the effectiveways to reduce car weight. However, the performance(such as crashworthiness, stiffness, and dent resistance)of part made of new material should be assured. Forexample, the front parts of a car are major energyabsorption parts in the process of car crash, so energyabsorption performance without affecting the safety ofpassengers should be assured in the design of front partsof a car. In this research, the bumper of the passengercar is studied under different materials but remainingits dent resistance.The mechanical properties of mild steel and highstrength steel are listed below (see Table 1).The evaluation index of dent resistance for bumperusing mild steel isPcr1 C1rs1t21:15When high strength steel is used to replace the mild steelremaining its primary shape and dent resistance per-formance, the new thickness t2of high strength steelcan be achievedt2ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiC1rs1C2rs2t1r:16From (16), the thickness of bumper that uses highstrength steel is gained and updated in the full car FEmodel. The deformation history of bumper using newmaterial is achieved after the car crash is re-simulatedwith updated part thickness (see Fig. 3).By simulation, the deformations of bumper made oftwo different kinds of material are similar in that plastichingeandtensionalplasticdeformationappearinthemid-dle part of bumper. And the energy absorption history isshown in the following for beam of the bumper. FromFig. 4 the difference of the energy absorption betweenTable 1Mechanical properties of two materialsMaterialDensity (g/cm3)E (GPa)lrs(MPa)Mild steel7.82100.3166High strength steel7.82100.3220Fig. 3. The deformation history of bumper using high strength steel.Fig. 4. Energy absorption time history of bumper beam.Y. Zhang et al. / Materials and Design 27 (2006) 646867twomaterialsissmall,about4.1%forbeamofthebumper,from which a conclusion can be drawn that itis feasible toreducethethicknessofthebumperpanelbasedonthedentresistance evaluation index studied in this research.4. ConclusionDent resistance performance of small curvature shal-low shell parts in automobile is studied in this paper,which enables the follows:1. Dent resistance stiffness under concentrated force isgiven for such parts.2. The critical load resulting in the local trivial dent inthe center of the shallow shell has been deduced,which in turn becomes the index to evaluate the dentresistance of automobile parts.3. The validity of evaluating index is proven by applyingthe developed rule to the lightweight design of bum-per system using high strength steel instead of mildsteel through crashworthiness simulation.References1 Yuxan Li, Zhongqin Lin, Aiqin Jiang, Guanlong Chen. Use ofhigh strength steel for lightweight and crashworthy car body.Mater Des 2003;24:17782.2 Yuxuan Li. Automobile body lightweighting research based oncrashworthiness numerical simulation. PhD thesis, Shanghai JiaoTong University, China; 2003.3 Zhu Shi-feng, Song Qi-feng. Research of CA1092 automotivebody lightening. Automob Technol Mater 2002;89:5862. inChinese.4 Jambor A, Beyer M. New carsnew materials. Mater Des1997;18:2039.5 Cheon SS, Lee DG, Jeong KS. Composite side door impact beamsfor passenger cars. Compos Struct 1997;38:22939.6 Li Dong-sheng, Zhou Xian-bin. The static and dynamic dentresistance of automobile steel sheet. J Plast Eng 2003;10:325. inChinese.7 Li Dong-sheng, Zhou Xian-bin. The analysis on sinking stiffnessof double curvature auto-body panel. Chin J Appl Mech 1998;15:1158.8 Nader A. On strength, stiffness and dent resistance of car bodypanels. J Mater Process Technol 1995;49:1331.9 Dicellello JA et al. Design criteria for the dent resistance of auto-body panels. SAE 1974:38997.10 Han Qiang, Huang Xiaoqing, Nin Jianguo. Advanced Plate andShell Theory. New York: Science Press; 2002.68Y. Zhang et al. / Materials and Design 27 (2006) 6468轻量化设计的汽车零部件用高强度钢来抗凹 张研 来新民 朱平 王吴荣摘要 轻巧耐撞性是汽车车身设计的两个重要因素。在这篇文章中，基于浅壳理论，表达抗凹刚度的双曲率扁壳是在集中载荷条件下取得的。该临界负荷导致当地琐碎的凹痕在该中心的浅壳被视为轻量级对汽车零部件的重要影响指数。本规则适用于轻量化设计的保险杠系统用高强度钢代替温和钢。耐撞模拟轻量级的一部分，证明了轻量化进程的有效性。关键词: 高强度钢 轻量 抗凹1、介绍 近年来，由于汽车保有量的急剧增长，大大影响了社会和人们的生活，这种情况带来了很多严峻的问题比如能源危机，环境污染。国际铝组织协会声明石油的消耗可降低8-10与减少约10的汽车重量。因此，汽车轻量化是节约燃料的一个基本方式。 为了减少汽车的重量，这又两个较好的方法。一种方法是重新设计汽车零部件优化其结构，通过使用细薄的、空心的、小型的和混合材料的零部件，来减轻汽车的重量。另一种是使用新的轻型材料，如今这种材料越来越多，如铝合金，高强度钢，复合材料都被广泛作为轻质材料以取代传统材料如低碳钢。这些材料可以显着的减轻汽车的重量。使汽车轻量化材料替换比优化结构更有效。根据引进的汽车安全法规，轻量化设计的车身中耐撞性和安全性被视为先决条件。高强度钢被广泛的应用于汽车上以代替传统的低碳钢。 高强度钢板可用于汽车车身来提高部件碰撞能量吸收能力和耐塑性变形能力。汽车体重可减少通过使其零部件用一个更薄厚度的高强度钢板取代低碳钢板来制造。与铝相比，镁，复合材料和高强度钢具有更好的经济性因为这些材料的原料和制作费用比较便宜。此外，高强度钢可直接应用到生产线上，包括成型，焊接，装配和油漆。经营成本节省了，因为没有必要对整个线路进行调整。 在车身外，有几个薄的金属板，其中大部分是浅水面板。凹痕阻力是有能力保持形状对沉没挠度和地方凹痕在外力的作用下。凹性汽车板成为汽车的一个重要方面和质量标准。因此，抗凹刚度的汽车板应在面板设计和制造过程中被测试和评估。一些报道的测试方法列举如下: 1）、在外力不变的情况下，测量位移沉没挠度的fp 2）、测试外力F到获得固定位移沉没偏转量 3）、在外力载荷作用下测试得边坡力位移曲线 在这篇文章中，第二种方法将被采用，该表达抗凹刚度双曲率浅壳是通过浅壳理论和集中负载的条件下得到的。该临界负荷导 致该中心浅壳琐碎的凹痕被视为凹性汽车零部件的重要评价指数。本规则适用于在第2条中，轻量化设计连年系统用高强度钢代替低碳钢与耐撞性仿真。2、双曲率浅壳的抗凹性分析2.1 浅壳的抗凹刚度分析壳牌与中表面特点可以分为三特征：厚度h，中面尺寸L，曲率半径r ，并满足的h / r1。当h/L1时，定义外壳为薄壳，如果在上述两条件满足的同时又满足Lr1，这个薄壳被认为是浅壳。如图1所示，平面x-y是浅壳中表面沿着z轴的投影。假设M是中表面上的任意一点，两平面QMN&PMN分别去平行OYZ和OXZ。边PM和QM可近似认为是垂直的因为中表面和平坦。同时，MN正交于中面。因此，MN,PM,QM可构成垂直参考系MPQN。其差额由正交坐标系统OXYZ可以忽略不计，同时PM和QM通过和来表示，该曲面坐标MPQN。图1假设M是Z轴上的一点，对中表面的详细分析方程如下：z=F(x,y) （1）由于是平坦的外壳，就有如下方程： （2）中面的曲率和挠度可近似至： （3）该中面的下载系数可沿和方向导出： （4）运用集中力P沿Z轴和忽略横向剪切力造成的影响，得到浅壳的平衡微分方程： （5）其中（0，0）是狄拉克-函数。浅壳的兼容性方程是： （6）其中 通过横向位移w来表达瞬时结果M1, M2和M12，浅壳在横向集中力下的基本方程： （7）其中N1是膜应力在X方向，N2是膜应力在Y方向，D表示浅壳的抗弯刚度。这是很难解决上述方程。据要立足现实，沉没的偏转将只集中就在小范围内左右对外力P ，所以无限大型浅水壳牌是假定在这项研究中。因为w，N1,N2关于X,Y轴对称，所有顺序衍生的w,N1,N2都无限接近于零，以下方程可通过傅立叶进行变换。 （8）其中： （9）从公式（8）我们可以得到。通过逆向傅立叶变换和极坐标转换,w，再根据极坐标系统我们可以得到： （10）把x=0,y=0带入式（8），这关系在偏转力fp和矩形浅壳的集中力P我们可以得到如下： （1
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